Superconducting materials are finding increasing use where strong, highly stable magnetic fields are required such as, e.g., in nuclear magnetic resonance spectroscopy, in high-resolution electron microscopy, and for deflecting and focusing high-energy particle beams. Also, as mentioned by T. Luhman et al., Metallurgy of Superconducting Materials, Academic Press, 1979, future applications of superconducting materials are likely in areas such as, e.g., the generation of power by magneto-hydrodynamic methods and by nuclear fusion, the separation of ores, the treatment of sewage, the purification of water, and the levitation of high-speed tracked vehicles. Considered most likely is the use of superconductors in electrical power generation facilities.
A great number of materials are known which become superconducting at temperatures below a certain critical temperature which is material-dependent and which is customarily denoted by T.sub.c. Among materials having a desirably high critical temperature are certain niobium compounds such as, e.g., Nb.sub.3 Al, Nb.sub.3 Ga, Nb.sub.3 Ge, Nb.sub.3 Sn, and Nb.sub.3 (Al.sub.0.8 Ge.sub.0.2); these compounds have critical temperatures in the vicinity of 17 degrees Kelvin and higher.
Since many high-T.sub.c superconducting compounds are brittle, special methods are needed for their manufacture into shaped articles and parts. For example, for the manufacture of niobium-aluminum and niobium-aluminum-germanium materials, high-temperature reaction methods have been proposed by R. L. Ciardella et al., "A Quench-Age Method for the Fabrication of Nb(Al) Superconductors", IEEE Transactions on Magnetics, Vol. MAG-13 (1977), pp. 832-833 and K. Togano et al., "An Improved Method for Fabrication of Nb.sub.3 (Al,Ge) Wire", IEEE Transactions on Magnetics, Vol. MAG-13 (1977), pp. 478-479. Another method, known as "bronze process" and suitable, e.g., for the manufacture of Nb.sub.3 Sn superconducting material is based on a solid state reaction at an interface between niobium and a copper-tin alloy. This reaction occurs, e.g., upon drawing niobium rods in a bronze matrix to wire dimensions and heating at a temperature in the range of 575-750 degrees Celsius.
While methods similar to the bronze process have been successfully applied to certain other niobium-based superconductor materials, no corresponding method has been available for the manufacture of suitably crystallized Nb.sub.3 Al material. (Owing to a high critical field, Nb.sub.3 Al is considered to be particularly suitable as a superconducting material.)
It has been hypothesized by L. R. Testardi et al., "Superconductivity in Some New Metastable Film Phases", Journal of Applied Physics, Vol. 45 (1974), pp. 446-451, that Nb.sub.3 Al is a contaminant in thin films of Nb.sub.0.67 Hf.sub.0.33 deposited on a hot sapphire substrate.